Method of forming cylinder liners



Oct. 31, 1944. R. E. SURTEES METHOD OF FORMING CYLINDER LINERS 2 Sheets-Sheet 1 Filed Aug. 8, 1939 0ct.31,1944.' URTEES. 2,361,434

METHOD OF FORMING CYLINDER LINERS Filed Aug. 8, 1959 2 Sheets-Sheet 2 INVENTOR A TORNEYS Patented Oct. 31, 1944 2,361,434 METHOD or FORMING CYLINDER LINERS V Robert E. Surtees, Milwaukee, Wis.

Application August 8; 1939, Serial No. 288,926 4 Claims. (Cl. 29-1564) The present invention relates to liners for cylinders of internal combustion engines and the like, and more particularly to liners adapted to be fitted in a cast metal cylinder block and form a bearing surface for the usual reciprocating piston.

In order to prolong the life and improve the operating efllciency and other desired characteristics of internal combustion engines, it has become a practice in the automotive field and in other applications of internal combustion engines to use a liner within the customary cast cylinder block. Another application of cylinder liners is made in rebuilding worn engines, wherein the engine cylinder walls as originally constructed were integral with the block, by reboring the cylinders to a dimension sufiicient to permit the fitting of liners therein, and inserting liners that will restore the dimensions of the cylinders to their original size. The liner is usually made of a harder material than the block but the material used may be selected because of other desired characteristics.

Cylinder liners may be classified in two general types, namely, the wet" and dry" types. The wet type derives its name from the fact that the liner as fitted within the bore of the cylinder block serves to define part of the enclosing wall for the passages through which cooling water is circulated in the cylinder block and which form the customary water jacket. In other words, in this type of construction the cooling water circulates directly in contact with the walls of the liner. In the dry type, the water jacket is completely enclosed within the cylinder block, out of contact with the cylinder liner, and the liner merely fits tightly within the cylinder bore.

Heretofore in making cylinder liners, centrifugal castings, sand castings, forgings and welded or seamless tubings have been used which in themselves are expensive and necessitate an unscratches, no matter how fine thefinish, and,

' since the grinding is performed on different pordue amount of finishing-grinding and honing before a liner properly proportioned to fit accurately within the cylinder block can be completed, Centrifugal castings must be heat treated and ground and usually machined; sand castings require thick walls which must be reduced and trued by machining and grinding; forgings involve a prohibitive expense, and welded or seamless tubings usually require an undue amount of truing and, when welded, must be ground to bring the thickness of the welded portion to the same dimension as the rest of the tubing. Grinding operations to which all of these types must be subjected sometimes leave grinding checks and tions of the liner at various times, the liner may have variations in wall thickness and in concentricity.

The present application relates both to a novel method of forming a light-walled highly finished cylinder liner method of making a cylinder liner of a precise uniform wall thickness throughout with the inand improved physical characteristics more fully described hereinafter. The method is peculiarly well adapted ior application to materials which may be hardened to an extreme degree compared to the liners now in use, and includes in certain of its more specific modifications a novel combination of working and hardening treatment steps which lead to the production of markedly superior and heretofore unappreciated results.

In addition to the objects and advantages above indicated, the invention makes it possible to use relatively thin sheet or strip material and to provide a liner of lighter gauge than heretofore practicable with consequent saving in material and improvement in heat transmitting characteristics.

Still further objects and advantages of my invention will be pointed out or indicated hereinits employment in practice.

As an aid in disclosing the invention,

according to the present invention;

'Fig. 4 is a cross-section through the rolling mandrel and associated rolls viewed on the line 4-4 of Fig. 3.

Fig. 5 is a top plan view of the lie with the rolling head removed;

Fig. 6 is a further view showing the grinding of the abutting edges of the shell; and

Fig. 7 is a view of the finished liner in elevation before fitting the same into a cylinder block.

In an illustrative embodiment of my invention I form a sheet of metal of the appropriate size and thickness into a roughly cylindrical shell with the abutting edges in approximate juxtaposition. This shell or body is then disposed within a specially formed jig or former and rolled upon the interior to make a smooth cylinder surface of the finish desired and to increase the surface density, while at the same time reducing the walls to a substantially uniform thickness throughout. The shell is then removed from the jig or former and hardened either throughout or locally on the inner wearing surface by any suitable method, such as by a hardening heat treatment, by case hardening, or by a nitrogen hardening process. After rolling and before hardening the opposed edges of the shell may be trued by placing the shell on an arbor and subjccting the edges to a broaching operation. As an alternative step or as supplementary to the broaching step, the shell may be placed upon an arbor after thehardening step and the opposed edges are then trued by a grinding operation. In any case the broaching or grinding or both is so conducted as to render the opposed edges of the shell capable of so coinciding one with the other or meeting in such contact that practically a solid cylinder is formed. The completed cylinder liner is thus a cylindrical shell or body having a cleft or split running lengthwise thereof and capable of being pressed together to form a substantially solid cylinder wall.

The application of surface hardening treatment to the rolled cylinder may require special preliminary and intermediary steps. For example, when a steel adapted to be surface hardened by nitriding is used it is usually advantageous to subject the steel preliminary to nitriding to a heat treatment adapted to bring the carbide constituents to a state of fine dispersion in the ferrite matrix, i. e., at least to a sorbitic state, and in somecases' prolongation of the heat treatment to produce a spheroidized state will be warranted. Heat treatment as ordinarly applied to produce either of these states usually causes some surface decarburization. Furthermore, sheet or strip steel intended to be shaped or further worked is usually formed by hot rolling, and this causes considerable surface decarburization. If the steel sheet or strip were used in the surface decarburized state, the final product would often be unsatisfactory in surface appearance or more susceptible to various forms of corrosive action. When such material is subsequently surface hardened without any intermediate or preliminary treatment designed to overcome the effects of the surface decarburization, the resulting hardened surface may have a tendency to spall or exhibit other undesirable characteristics. In preparing hot worked or heat treated steel for surface hardening, and particularly for nitriding, it has been a the practice to subject the heat treated steel to a preliminary grinding treatment before nitriding.

One of the important advantages of the present invention and one to which certain of the improved results are believed in a large measure to be attributed resides in the fact that the cylinder wearing surface is not around, and therefore does not have the drawback that grinding scratches or scorlngs are present. Moreover. the special rolling treatment of the present process makes it unnecessary to grind away any surface portion to counteract decarburizing caused by hot rollin or occurring in the preliminary heat treatment. The rolling treatment serves to densify the surface portions of the cylinder liner and render it particularly amenable to surface hardening processes. For example, when nitriding is employed subsequent spalling of the nitrided case is avoided.

A further feature of my invention resides in the provision of a jig having a precise circular dimension and the association therewith of a rolling mechanism by means of which the liner blank is rolled while held in the jig to an extremely close tolerance asrespects its internal diameter, while at the same time so controlling the rolling as to produce a liner with walls of substantially uniform thickness.

I have found that it is extremely important that the cylinder liner shall not only present a truly cylindrical wearing surface for contact with the piston but also that it shall be of uniform wall thickness. This is important as insuring uniform heat transmitting characteristics, a factor of great importance in the operation and longevity of an internal combustion engine equipped with cylinder liners.

While it is possible to obtain a uniform wall thickness using known types of rolling devices in combination with a jig of precise internal dimension and such a combination may be used in practising my improved method to produce my improved liner, I have developed and prefer to use the special form of rolling mechanism hereinafter more particularly described and illustrated in Figs. 3 and 4. This mechanism is characterized by the provision of rolls of a. length at least as great as the liner, which insures that the rolling pressure can be exerted simultaneously throughout the length of the cylinder and with the rolls traveling in a circular path. This facilitates the rolling of the walls of the liner to a precise internal dimension and to a. uniform wall thickness.

The improved liner made according to my invention may advantageously be produced from sheet or strip metal of 0.040" thickness, which has been formed by hot rolling in the usual manner, then pickled and given one or two cold passes. As thus rolled the material will usually be too hard for the subsequent forming operations, and, therefore, I subject the sheets or strips to an annealing treatment. In this treatment the metal is advantageously heated to a temperature of around 1325 F. and held at this temperature for a sufficient period to insure that the carbides are brought to a spheroidized state. In some cases and with some steel compositions it may be desirable to so conduct the heat treatment as to bring the metal to a uniform sorbitic state but usually it will suffice if spheroidizing is accom- I 4. The blank is passed between guide rolls l2-| 2, and the forward end of. the blank is turned Over by engagement with bending roll I4. As the blank continues through the bending device it is bent into cylindrical shape.

Where this roller method of forming the cylin der isused, it will be noted that the shell or body member thus formed has flattened end portions I 6 and i1 adjacent the inwardly turned edge portions l8 and I9. These flattened portions will be rolled to conform to the desired shape of the cylinder wall in the subsequent rolling operation. The shell or body member is then inserted in the jig for the special rolling operation.

The jig or former 22 that I employ for supporting the shell during the rolling operation is made with side walls that are heavy and rugged enough to withstand a'rolling operation upon the interior thereof without stretching .or becoming deformed in any manner. Likewise, the interior wall surface of the jig is preferably hardened and ground or honed to prevent its being stretched or distorted by the insertion therein and removal therefrom of the shell. It is important that care be taken to insure that the inside dimension of the jig shall be truly cylindrical. The jig may be made of any 'material having the requisite strength and other desired properties. A cast iron or cast steel containing suitable amounts of chromium and nickel serves the purpose very well.

In the form shown in Figs. 3 and of the drawings, the jig comprises a base 24 housing a thrust bearing 26 and supporting the main body of the jig 28. Fitted in a recess 30 adjacent the end of the jig body and resting upon an upwardly extending portion 32 of the base 24 is a ring 34 which is of somewhat smaller inside diameter than the body 28 and serves to provide a shoulder 36 upon which the shell rests during the rolling operation. The ring ishardened, ground and lapped on all surfaces. The jig body 28 is likewise hardened, ground and lapped or otherwise specially finished on its interior surface to produce a very smooth cylindrical surface. The liner shell is inserted in the jig with its lower end resting on the upper edge of the ring 34. The ring is ground to such size as to provide sufficient clearance to insure that the rollers, when operating on the liner shell, are out of contact with the ring. For example, if a liner is being rolled from .040" material the ring may extend inwardly .010" beyond the inner wall of the jig, thusproviding a clearance of .030" between the rollers and the ring at the beginning of the rolling operation.

When the liner shell has been placed in the jig and rests on the shoulder 36, a cap or retaining member 38 is placed on the head of the jig and tightened down by eye bolts 40 and nuts 42 cooperating with radially extending lugs 44 on the cap 38. The eye bolts 40 are carried by a collar 46 which is shrunk on or otherwise secured adjacent the head of the jig. The eye bolts are retained on pivots 48 mounted in circumferentially spaced slots 50 and adapted to be swung outward when the cap 38 is removed. The cap 38 is hardened, ground and lapped on its top and bottom to provide parallel bearing surfaces 52 and 54. The lower bearing surface 52 engages the upper edge of the liner shell and holds it in position against the shoulder 36 during the rolling operation. The outer part of this bearing surface also rests upon the upper end of the jig which is similarly hardened, ground and lapped. The

upper bearing surface 54 serves to limit the extent of movement of the mandrel as will be explained mandrel 64 beyond the outer peripheral surface further in describing the rolling head.

The jig is made of an internal circular dimension somewhat larger than the outside diameter of the finished liner so as to take care of the circular stretch or extension of the material when rolled, and to prevent the opposed edges of the liner from coming together in the rolling operation. If this takes place stresses will be created which will cause the edges to turn inward when the liner is removed from the jig. I have found that in designing a jig to roll liners of a 4.50 inside diameter from strip material having a thickness as received from the mill of .042" in the middle of the strip tapering to-.041" at the edges, a jig having an inside diameter of 4.7647" will insure satisfactory results when a reduction of the Wall thickness to a uniform thickness of .040 is to be made.

A jig properly sized to form the shell or body member to its final cylindrical shape having been provided, the shell is fitted therein by pressure or other means and is ready for the rolling operation. While the rolling or forming operation may be carried on in several known ways, I shall describe it as carried on with a'special rolling head developed by me and adapted to cooperate with my special form of jig above'described in attaining the improved results. 'As shown in Figs. 3 and 4, the rolling head 50 comprises a cage 62 which fits over and is in sliding engagement with a slightly tapered mandrel 54, provided with a squared shoulder portion 66 adapted to establish driving connection with not shown.

gitudinally extending slots 68 equally spaced in the side walls of the cage and having inwardly flaring side walls 10. These slots retain a series of rollers 12 which are pressed outward by the of the cage and provide a series of parallelly arranged rolling surfaces adapted to roll upon,

densify and smooth the inner wall surface of the liner shell. The rollers are adjusted inwardly and. outwardly in their retaining slots as desired by bringing about relative longitudinal movement of the mandrel and cage. In order to prevent the cage and the associated rollers from dropping off the end of the mandrel when it is being inserted into or removed from the jig, I provide a nut 14 which is screwed onto the end of the mandrel after the cage and rollers have" been assembled on it.

At the top of the mandrel there is provided a collar 16 adapted to be adjusted lengthwise of the mandrel on the threaded portion 1-8. This collar 16 is provided with a down-turned rim portion adjacent its periphery and having a lower surface portion 82 which is hardened, ground and lapped to form a smooth surfaceadapted to contact with the similarly formed surface 54 on the head of the jig when the liner has been rolled to the desired extent. A locking nut 84 is associated with the collar 16.

In carrying out the rolling operation, the liner shell or flange having first been inserted in the jig as above described, the rolling head is then inserted with the lower end 86 of the cage 62 resting upon the thrust bearing 26. 16 is adjusted with that amount of clearance from the bearing surface 54 at the top of the jig that power means,

The collar desired reduction in thickness of the liner in the rolling operation. The rolling operation is then commenced and continued until the face 82 of the collar 86 comes into contact with the bearing surface 54, whereupon further reduction of the liner will be arrested. It will be understood that the mandrel is given a downward endwise thrust during rolling so as to gradually press the rollers further outward as the liner is smoothed and condensed. On completion of the rolling operation the rolling head is withdrawn from the jig. The nuts are loosened, permitting the eye bolts 40 to be swung outwards. The head 38 is then lifted off, permitting the liner to be removed by hand.

Once the collar has been adjusted to provide the clearance determined to be right for rolling a given liner, the operations may be repeated indefinitely by relatively unskilled workmen, since the adjustment determines the extent of the rolling operation and insures that each liner will be brought to the same uniform thickness.

As indicated, the lower end 86 of the cage 62 is supported by the thrust bearing 26 and confined against lateral movement by the ring 34. At the same time the rollers extend parallel to the length of the liner and are caused to travel in a truly circular direction. These arrangements insure that the wall thickness of the liner will be substantially uniform throughout and free from the slight, but nevertheless noticeable, irregularities that are produced when rolling according to the prior procedures.

The mandrel is shown as hollow to save weight but it will be understood that it may be solid if desired. Likewise, the number of rollers may be varied more or less provided they are equally spaced circumferentially in the cage.

The desired wall thickness and finish of the interior of the liner shell having been obtained in the rolling operation, it is then usually desirable to subject the liner to a hardening treatment. As before indicated, any suitable hardening treatment may be used to produce in the inner or bearing surface of the liner the degree of hardness required to withstand the strain and wear to which it is intended to be put. A hardening procedure that I have found to be particularly desirable and the one that will be described by way of example is that of nitriding.

when the liners are to be nitrided they will, of course, be made of a steel alloy of one of the types recognized as especially suitable for nitriding, such as for example. one of the steel alloys of the type known commercially as Nitralloy." The steel will have been brought to the physical state most suitable for nitriding by heat treatment given preliminary to the rolling. The rolling treatment serves to cold work and densify the wall surface. This is important when nitriding, particularly if in its earlier treatment the steel has suffered from decarburization in its surface portions, as is usuallythe case.

The nitriding treatment will usually be confined to the inner wall surfaces since these are the only ones that will be subjected to wear. However, the nitriding of the outside wall of the liner is not precluded, and in some situations may be of advantage, as for example, when the liner is to be used in a wet type of cylinder block, since the nitriding of the outer surface will increase resistance to corrosion,

In order to insure that the juxtaposed edges l8 and W of the cylinder shall be capable of forming a close fit when the liner is inserted in the cylinder block, it is necessary that they be ground carefully and gauged with care. If desired, the edges may be trued by broaching after the rolling operation and before hardening, but in any event it will be desirable to give the edges a final grinding treatment. For grinding purposes the shell ll may be fitted in an arbor or holding formilll having a groove or channel therein so that the cleft or split 2| will be disposed opposite to the groove. A grinding wheel 92 may then be used to true the edges l8 and [9 to the desired dimension. The grinding operation may take place before the hardening step if sufficient care is taken in the hardening process. The grinding process may have to be repeated, however, so I prefer to make this the last step in my method.

When the liner is finished as above, the juxtaposed edges IG and I9 normally spring slightly apart and remain in spaced relationship unless pressed towards one another. However, if the operations have been carefully controlled in the manner above described, these edges will meet in a close, practically fluid-tight fit when the liner is inserted into a cylinder opening that has been previously carefully bored or ground to size. It is thus possibie to form a substantially perfect bearing and compression cylinder wall. The substantial coincidence of the cleft forming edges l8 and I9 insures a smooth and hardened surface lmmg giving long wear and one which may be removed and inserted with comparative ease. The liners may be inserted into the cylinder openings and caused to assume a close lit by known methods, for example, by expanding the cylinder openings by heating the cylinder block, then inserting the liners and thereafter shrinking the walls of the cylinder openings around the liners.

It will be understood that the procedure may be modified in various respects and that the apparatus employed may likewIse take a diiierent form from that employed herein. Accordingly, the invention is not to be deemed as limited by the specific disclosure other than as indicated by the appended claims.

This application reproduces in part together with add tional subject matter my application Serial No. 736,376, filed July 21, 1934, which became forfeited July 14, 1939.

Iclaim:

The method of forming a cylinder liner, which comprises forming a metal sheet into a substantially cylindrically-shaped body member having inwardly turned edges in opposed relat onship, disposing said member in a jig having a precise circular dimension slightly larger than that desired for the outside dimension of said lmer, then applying positive, unyielding rolling pressure against the nner wall of said member to condense the surface portions thereof and effeet a substantial reduction in the wall thickness, and continuing this treatment until the wall has been brought to a uniform thickness and the desired finish is obtained but discontinung said treatment before the liner has been extended circumferentialiy suflicient to bring said edges into pressure contact.

2. The methcd of forming a cylinder liner, which comprises form mg a metal sheet into a substantially cylindrically-shaped body member having inwardly turned edges'in opposed relationship, disposing said member in a jig having a precise circular d mension, then applying positive, unyielding rolling pressure against the inner wall of said member at circumferentially spaced points simultaneously to condense the surface portions thereof, said rolling pressure at each point being exerted by' rolls extending throughout the entire length of said cylinder, causing the rolls to travel along said inner Wall in a circular path,- and continuing this treatment until the wall has been brought to a uniform thickness and the desired finish is obtained.

3. The method of forming a cylinder liner, which comprises iforming a metal sheet into a substantially cylindrically-shaped body member having inwardly turned edges in opposed relationship, dispos ng said member in a jig having a precise circular dimension slightly larger than that desired for the outside dimension of said liner, then applying positive, unyield'ng rolling pressure against the inner wall of said member at circumferentially spaced points simultaneous- 1y to condense the surface portions thereof, said rolling pressure at each point being exerted by rolls extending throughout the entire length of said cylinder, causing the rolls to travel along said inner wall in a circular path, and cntinuing this treatment until the wall has been brought to a uniform thickness and the desired finish is obtained but discontinuing said treatsubstantially cylndrically-shaped body member having inwardly turned edges in opposed relationship, disposing said member in a jig having a precise circular dimension slightly larger than that desired for the outs'de dimension of said liner, confining the ends of said liner so as to prevent lengthwise extension of the liner in the subsequent rolling operation, then applying rolling pressure against the inner wall of said member at circumferentially spaced po'nts simultaneously to condense the surface portions thereof, said roiling pressure at each point being exerted throughout the entire length of said cylinder, causing the rolls to travel alon said inner wall in a circular path, and continuing this treatment untl the wall has been brought to auniform thickness and the desired finish is obtained but discontinuing said treatment before the liner has been extended circumferentially sufficient to bring said edges into pressure contact.

ROBERT E. SURTEES. 

